White Band disease has devastated the staghorn coral Acropora cervicornis in recent decades, and it continues to impinge upon restoration efforts. The etiological agent(s) remain unknown as Koch’s postulates have yet to be satisfied, but disease may originate when opportunistic pathogens in the surface mucus layer exploit a stressed host. Using 16s rRNA sequencing, differences in the taxonomic diversity and relative abundances of bacteria within the mucus of A. cervicornis were documented between colonies of the same genotype, genotypes (n=8) categorized as having either high or low WBD susceptibility, and during a transplantation event. A. cervicornis colonies suspended from midwater PVC trees via monofilament were sampled for mucus, after which half of the sampled colonies were relocated to the unconsolidated sediments below. Temporal changes in the microbiome of the pelagic and benthic corals were then monitored by sampling the same apical tip over time. Incidentally, all benthic colonies for this experiment became afflicted with WBD; thereby differences in healthy vs. diseased colonies and the effects of disease progression on the microbiome were documented. Water was sampled concurrently with all mucus experiments to resolve the degree of commonality in bacterial species between the two environments, and sediments were sampled in the transplant experiment to determine if sediments may act as a pathogen reservoir. In addition, sediment samples were collected to assess site and temporal differences in the benthic microbiome along a nearshore to offshore transect off Key Largo, Florida. Irrespective of the inclusion of water operational taxonomic units (OTUs), no differences between colonies of the same genotype were observed with regards to the bacterial communities sampled from mucus in either alpha diversity metrics [species richness, Shannon, Inverse Simpson] or phylogenetic relatedness as determined by weighted unique fraction (UniFrac) were detected between colonies. However, differences were observed in the Bray-Curtis dissimiliarity matrices based on relative abundance and presence/absence of either [with and without water OTU] scenarios. Bacterial communities associated with different coral genotypes differed in species richness and Inverse Simpson in both water scenarios, as did weighted UniFrac and Bray-Curtis relative abundance and presence/absence transformed dissimilarity matrices. Alpha diversity of mucus bacteria was similar between corals of different disease-susceptibilities when water OTUs were either included or excluded, except for the Inverse Simpson index upon removal of water OTUs. Removal of aqueous bacteria also revealed significant differences between disease-susceptibility groups in Bray-Curtis relative abundance and presence/absence dissimiliarity values that was not detected with the incorporation of water OTUs. Regardless of the presence of water OTUs, weighted UniFrac was similar between corals of different disease susceptibilities. Most notably, dispersion increased in the microbiome of coral genotypes with high disease susceptibility in all cases except for the relative abundance transformed Bray-Curtis dissimilarity matrix when water OTUs were incorporated. This finding is in accordance with the Anna Karenina Principle, which states that loss of microbial regulation leads to an unpredictable microbiome in diseased individuals. In the sediment experiment, location was the only factor influencing microbiome composition. These findings may be due to the short duration of the experiment and differences between the carbonate content of the sediments and hydrological regimes between sites.

South Florida contains one of the largest subtropical wetlands in the world, and yet not much is known about the microbes that live in these surface waters. These microbes play an important role in chemical cycling and maintaining good water quality for both human and ecosystem health. The hydrology of Florida’s surface waters is tightly regulated with the use of canal and levee systems run by the US Army Corps of Engineers and The South Florida Water Management District. These canals run through the Everglades, agriculture, and urban environments to control water levels in Lake Okeechobee, the Water Conservation Areas, and the surrounding farm lands. I hypothesized that there would be noticeable shifts in the microbial communities (also known as “microbiomes”) at the agriculture and urban sites due to anthropogenic influences such as agricultural and sewage runoff. It is also hypothesized that the diversity and stability of these sites will differ from the natural environment Grassy Waters Preserve (GWP), which we studied as a control. The northern section of GWP is a rain-fed Everglades ecosystem with little influence from manmade canal systems, so GWP can represent wetlands before human influences. High-throughput 16s rRNA sequencing was conducted on 112 GWP, canal, and agricultural water samples taken over a one-year period from September 2016 to November 2017. Data were processed in Qiime2 using DADA2 and resulted in 67732 unique taxa. Nineteen metadata factors were measured for 87 of the sampling points to investigate environmental effects. These factors explained 25% (r2=0.25, p=0.002) of the variation between sample locations. Conductivity was found to have the highest effect on microbial diversity (r2=0.078, p=0.002) while latitude and month also significantly influenced the microbial makeup. Urban and agricultural sites were found to have higher stability with lower variation in microbiomes over the course of study. The GWP site was found to have a high seasonality, probably due to its dependence on rain. The most abundant taxa for all sites (urban, agriculture, and control) were; family Spirochaetaceae, phylum Actinobacteria, and family Burkholderiaceae, respectively. Contamination of GWP and canal sites was also investigated using SourceTracker code. Intracoastal waters that receive canal water were found to be heavily influenced in the peak wet season when there is high flow through from the canals. GWP had little influence from farm lands compared to a high influence of agriculture on the urban sites.

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Various disorders closely linked to gut dysbiosis have been associated with poor dietary patterns. Dietary prebiotic fibers play an essential role in modulating the gut microbiome by enhancing the abundance of beneficial microorganisms and improving the production of short-chain fatty acids. Arabinoxylan (AX) is a major component of most dietary fibers and has been shown to exhibit potential prebiotic properties and modulate gut microbiome composition. This study aimed to investigate the in vitro impact of bioengineered wheat arabinoxylan on depression-inversely linked gut microbes and human gut microbiome diversity and metabolism. This study demonstrates the ability of bioengineered AX to stimulate the growth of depression-inversely linked gut bacterial species (Faecalibacterium prausnitzii and Lacticaseibacillus rhamnosus LGG). On the microbiome composition, the bioengineered AX induced an increased abundance of beneficial bacterial taxa (Bacteroides, Bifidobacterium, Anaerofustis, and Eubacterium) compared to the control and native AX. These effects on microbes translated into significant metabolic activity and produced primary SCFAs (acetate, butyrate, and propionate). The findings from this study suggest that bioengineered wheat arabinoxylan could be considered a promising strategy for fostering next-generation prebiotics targeting depression-inversely linked gut microbes and also supports the structure-function relationship between AX and the human gut microbiome.

This review focuses on the roles antioxidants and pro-oxidants in colorectal cancer (CRC). Considerable evidence suggests that environmental factors play key roles in the incidence of sporadic CRC. If pro-oxidant factors play an etiological role in CRC it is reasonable to expect causal interconnections between the well-characterized risk factors for CRC, oxidative stress and genotoxicity. Cigarette smoking, a high dietary consumption of n-6 polyunsaturated fatty acids and alcohol intake are all associated with increased CRC risk. These risk factors are all pro-oxidant stressors and their connections to oxidative stress, the intestinal microbiome, intestinal microfold cells, cyclooxygenase-2 and CRC are detailed in this review. While a strong case can be made for pro-oxidant stressors in causing CRC, the role of food antioxidants in preventing CRC is less certain. It is clear that not every micronutrient with antioxidant activity can prevent CRC. It is plausible, however, that the optimal food antioxidants for preventing CRC have not yet been critically evaluated. Increasing evidence suggests that RRR-gamma-tocopherol (the primary dietary form of vitamin E) or other "non-alpha-tocopherol" forms of vitamin E (e.g., tocotrienols) might be effective. Aspirin is an antioxidant and its consumption is linked to a decreased risk of CRC.

PURPOSE OF REVIEW: This review article aims to explore the GI changes induced by SARS-CoV-2 and how gut microbial homeostasis can influence these changes and affect the lung-gut axis and its relationship with the induction of the cytokine release syndrome in severe COVID-19 patients. RECENT FINDINGS: Coronavirus disease 2019 (COVID-19) affects not only the respiratory system but can produce multi-systemic damage. The expression of angiotensin-converting enzyme 2 (ACE-2) receptors in the gastrointestinal (GI) tract, the high prevalence of GI symptoms in severely ill COVID-19 patients, and the abnormalities described in the gut microbiome in these patients have raised concerns about the influence of GI tract as a risk factor or as a potential modulator to reduce the severity of COVID-19. Understanding the mechanisms by which gut dysbiosis may influence viral transmission and disease progression in COVID-19 may help in shaping how accessible therapies, like diet modulation, can potentially help beat the devastating consequences of COVID-19.

京都大学 / 新制・課程博士 / 博士(農学) / 甲第23934号 / 農博第2483号 / 新制||農||1089(附属図書館) / 学位論文||R4||N5369(農学部図書室) / 京都大学大学院農学研究科応用生物科学専攻 / (主査)教授 廣岡 博之, 教授 松井 徹, 教授 吉田 天士 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM